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Let's say that Apple's lower-end products are cutting into sales of the high-end iStuff. Would that be a signal to buy or sell component suppliers? The answer might surprise you.

When Cupertino's shares took a 4.5% plunge on Friday, it brought a whole bunch of peripheral stocks along for the ride. Some fell even harder than Apple.

Audio-chip supplier Cirrus Logic (NASDAQ: CRUS) lost as much as 7.6%. Wireless-radio producer Skyworks Solutions (NASDAQ: SWKS) took an 8.5% dive. Camera-chip designer OmniVision Technologies (NASDAQ: OVTI) lost 3.5% at most, and even mighty Qualcomm (NASDAQ: QCOM), which ships a number of chips in every iPad and iPhone, dropped 5.2%. And the beat goes on.

This is the downside to riding Apple's powerful coattails. When Apple jumps, so do Cirrus and Skyworks. But when Cupertino drops, OmniVision and Qualcomm take a fall, too.

And that's what's happening here. In separate researchnotes, two analyst firms slashed their iPhone unit forecasts based on order cuts they've seen while talking to Chinese supply-chain players. Jefferies analyst Peter Misek posits that Apple may have built too many iPhones in the current quarter while UBS analyst Steve Milunovich saw the iPhone 5 doing worse than the previous generation's iPhone 4S.

Both firms took great pains to explain that Apple isn't dead or even dying, but the prospect of "peak iPhone" must be unnerving to Apple investors.

I would add that Apple's margins and bottom-line profits would be damaged if consumers start looking for lower-cost alternatives. Cupertino would obviously rather sell iPad 3 and 4 rather than the iPad Mini and graybeard iPad 2, because the newer products carry much wider margins. The same goes for iPhone 5 versus older and cheaper iPhone 4S models.

But many of its component suppliers really don't care. Some Qualcomm and Cirrus chips haven't changed at all from one generation to the next, and a unit is a unit is a unit. So if Apple has started to cannibalize itself, this could be a great time to start positions in many of its hangers-on.

Playing Apple by proxy still seems like the safest bet to me. Qualcomm and Cirrus get my vote as the Apple suppliers most likely to thrive if Cupertino goes haywire, but your mileage may vary.